Luminosity distributions within rich clusters — II. Demonstration and verification via simulation     

Simon P. Driver  Warrick J. Couch  Steven Phillipps  & Rodney Smith 《Monthly notices of the Royal Astronomical Society》1998,301(2):357-368

We present detailed simulations of long-exposure CCD images. The simulations are used to explore the validity of the statistical method for reconstructing the luminosity distribution of galaxies within a rich cluster, i.e., by the subtraction of field number-counts from those of a sight-line through the cluster. In particular, we use the simulations to establish the reliability of our observational data to be presented in Paper III. Based on our intended CCD field-of-view (6.5 × 6.5 arcmin²) and a 1σ detection limit of 26 mag arcsec⁻², we conclude that the luminosity distribution can be robustly determined over a wide range of absolute magnitude (−23 <  M _R  < −16) provided: (a) the cluster has an Abell richness 1.5 or greater; (b) the redshift of the cluster lies in the range 0.1 <  z  < 0.3; (c) the seeing is better than FWHM 1.25 arcsec, and (d) the photometric zero-points are accurate to within Δ m  = ± 0.12. If these conditions are not met, then the recovered luminosity distribution is unreliable. Finally, although the method clearly has limitations, within these limitations the technique represents an extremely promising probe of galaxy evolution and environmental dependences.  相似文献   

A test of independence for stratigraphic sequences with respect to embedded Markov chains     

Sture Holm  Irene Isaksson  Rodney Stevens 《Mathematical Geology》1986,18(6):551-561

Identification of cyclic sequences gives valuable insight into depositional associations of stratigraphic facies. An embedded Markov chain is a reasonable general model for facies transitions. But a model with independent random occurrences of facies is not an appropriate null hypothesis to be tested to show the presence of cycles because of definitional restriction in transition observations to only those between different facies. This is a common stratigraphic situation and the problem has been raised recently by several authors. We present here a test statistic for null hypothesis derived from the concept of partial independence and inherent to the model of embedded Markov processes.  相似文献   

A stock rebuilding algorithm featuring risk assessment and an optimization strategy of single or multispecies fisheries     

Groger  Joachim P.; Rountree  Rodney A.; Missong  Martin; Ratz  Hans-Joachim 《ICES Journal of Marine Science》2007,64(6):1101-1115

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Wetting and drying in coastal flows     

Rodney J. Sobey 《Coastal Engineering》2009,56(5-6):565-576

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Optimal transfers between unstable periodic orbits using invariant manifolds     

Kathryn E. Davis  Rodney L. Anderson  Daniel J. Scheeres  George H. Born 《Celestial Mechanics and Dynamical Astronomy》2011,109(3):241-264

This paper presents a method to construct optimal transfers between unstable periodic orbits of differing energies using invariant manifolds. The transfers constructed in this method asymptotically depart the initial orbit on a trajectory contained within the unstable manifold of the initial orbit and later, asymptotically arrive at the final orbit on a trajectory contained within the stable manifold of the final orbit. Primer vector theory is applied to a transfer to determine the optimal maneuvers required to create the bridging trajectory that connects the unstable and stable manifold trajectories. Transfers are constructed between unstable periodic orbits in the Sun–Earth, Earth–Moon, and Jupiter-Europa three-body systems. Multiple solutions are found between the same initial and final orbits, where certain solutions retrace interior portions of the trajectory. All transfers created satisfy the conditions for optimality. The costs of transfers constructed using manifolds are compared to the costs of transfers constructed without the use of manifolds. In all cases, the total cost of the transfer is significantly lower when invariant manifolds are used in the transfer construction. In many cases, the transfers that employ invariant manifolds are three times more efficient, in terms of fuel expenditure, than the transfer that do not. The decrease in transfer cost is accompanied by an increase in transfer time of flight.  相似文献   

Plasticity,Not Adaptation to Salt Level,Explains Variation Along a Salinity Gradient in a Salt Marsh Perennial     

Christina L. Richards  Susan N. White  Mary Anne McGuire  Steven J. Franks  Lisa A. Donovan  Rodney Mauricio 《Estuaries and Coasts》2010,33(4):840-852

Evolutionary ecologists have long been intrigued by the fact that many plant species can inhabit a broad range of environmental conditions and that plants often exhibit dramatic differences in phenotype across environmental gradients. We investigated responses to salinity treatments in the salt marsh plant Borrichia frutescens to determine if the species is responding to variation in edaphic salt content through phenotypic plasticity or specialized trait response. We grew seedlings from fruits collected in high- and low-salt microhabitats, assigned seedlings to high- and low-salt treatments in a greenhouse, and measured traits related to salt tolerance. All traits were highly plastic in response to salinity. Plants from the two microhabitats did not differ in trait means or respond differently to the treatments. These results suggest that environmental differences between the two microhabitats are not creating genotypes adapted to high and low salt levels. In addition, despite evidence for variation in allozyme markers in this population, there was no significant genotypic variation (family effect) in any of the trait means measured across microhabitats. There was variation in plasticity for only leaf Na and leaf B concentration. The high degree of plasticity for all traits and the lack of differences among microhabitats across the salinity gradient suggest plasticity in many traits may be fixed for this species.  相似文献   

Submarine mass-wasting deposits as an indicator of the onset of foreland thrust loading—Late Permian Bowen Basin, Queensland, Australia     

Christopher R. Fielding  Christopher J. Stephens  & Rodney J. Holcombe 《地学学报》1997,9(1):14-18

In the eastern part of the Permo-Triassic Bowen Basin of Queensland, Australia, a transition from passive, thermal subsidence to flexural (foreland basin) subsidence is recorded within the Upper Permian stratigraphy. Two coarse-grained intervals containing deposits of mass-wasting processes occur within an otherwise siltstone-dominated succession over 1500 m thick (the Moah Creek Beds and equivalents). These intervals can be traced over at least 350 km north–south, along the structural eastern margin of the basin. The lower of the coarse-grained intervals is spectacularly exposed in the banks of the Fitzroy River, west of Rockhampton. Here, interbedded sandstones and siltstones of marine shelf origin are abruptly truncated by a mudrock succession containing evidence of slumping and contemporaneous magmatic activity. This unit passes up-section into packages of mass-flow conglomerates and diamictites, interpreted to have formed on an unstable submarine slope. The character of the mass-flow deposits, their stratigraphic position and lateral extent are interpreted in terms of destabilization of a sloping marine surface by pulsed, subsurface thrust propagation.  相似文献   

Petrogenesis of Na-rich paralava formed by methane flares associated with mud volcanism, Altyn-Emel National Park, Kazakhstan     

Rodney Grapes  Ella Sokol  Svetlana Kokh  Olga Kozmenko  Ilia Fishman 《Contributions to Mineralogy and Petrology》2013,165(4):781-803

High-Na slag-like rocks (paralava) with 4.5–11 % Na₂O from the Altyn-Emel mud volcanic field, Kazakhstan, are the products of melting of sediment + salt mixtures by methane flares associated with mud extrusion. The main minerals of the paralavas are diopside and wollastonite which have quench morphologies. Other high-temperature phases (crystallizing from melt and vapour phase) are tridymite, cristobalite, chlorapatite, alkali feldspar, pyrrhotite, native iron and silicon, iron phosphides, titanite, rutile, and carbon. The paralavas lack the Na–Ca silicates devitrite and combeite, but have high-Na and Na–K glasses that have not been homogenized despite low viscosities of <10^?3.5 Pa s. The large number of ignition foci in the Altyn-Emel mud volcano field indicates gas venting from small, shallow reservoirs. The methane flares are inferred to have been small and the fire events short-lived. Fires were extinguished once overpressure released during eruption, methane venting stopped and melted rocks rapidly quenched. The periodicity of eruptions and methane flaring most likely depends on the recurrence of earthquakes (M < 5) which are frequent in this tectonically active area.  相似文献   

The Boliden gold-rich volcanogenic massive sulfide deposit, Skellefte district, Sweden: new U–Pb age constraints and implications at deposit and district scale     

Patrick Mercier-Langevin  Vicky McNicoll  Rodney L. Allen  James H. S. Blight  Benoît Dubé 《Mineralium Deposita》2013,48(4):485-504

The Boliden deposit (8.3 Mt at 15.9 g/t Au) is interpreted to have been formed between ca. 1894 and 1891 Ma, based on two new U–Pb ID-TIMS ages: a maximum age of 1893.9?+?2.0/?1.9 Ma obtained from an altered quartz and feldspar porphyritic rhyolite in the deposit footwall in the volcanic Skellefte group and a minimum age of 1890.8?±?1 Ma obtained from a felsic mass-flow deposit in the lowermost part of the volcano-sedimentary Vargfors group, which forms the stratigraphic hanging wall to the deposit. These ages are in agreement with the alteration and mineralization being formed at or near the sea floor in the volcanogenic massive sulfide environment. These two ages and the geologic relationships imply that: (1) volcanism and hydrothermal activity in the Skellefte group were initiated earlier than 1.89 Ga which was previously considered to be the onset of volcanism in the Skellefte group; (2) the volcano-sedimentary succession of the Vargfors group is perhaps as old as 1892 Ma in the eastern part of the Skellefte district; and (3) an early (synvolcanic) deformation event in the Skellefte group is evidenced by the unconformity between the ≤1893.9?+?2.0/?1.9 Ma Skellefte group upper volcanic rocks and the ≤1890.8?±?1 Ma Vargfors sedimentary and volcanic rocks in the Boliden domain. Differential block tilting, uplift, and subsidence controlled by synvolcanic faults in an extensional environment is likely, perhaps explaining some hybrid VMS-epithermal characteristics shown by the VMS deposits of the district.  相似文献   

Comparison of low-energy lunar transfer trajectories to invariant manifolds     

Rodney L. Anderson  Jeffrey S. Parker 《Celestial Mechanics and Dynamical Astronomy》2013,115(3):311-331

In this study, transfer trajectories from the Earth to the Moon that encounter the Moon at various flight path angles are examined, and lunar approach trajectories are compared to the invariant manifolds of selected unstable orbits in the circular restricted three-body problem. Previous work focused on lunar impact and landing trajectories encountering the Moon normal to the surface, and this research extends the problem with different flight path angles in three dimensions. The lunar landing geometry for a range of Jacobi constants is computed, and approaches to the Moon via invariant manifolds from unstable orbits are analyzed for different energy levels.  相似文献